POS1232 EFFECT MODIFICATION OF CANCER ON THE ASSOCIATION BETWEEN DYSPHAGIA AND MORTALITY IN EARLY IDIOPATHIC INFLAMMATORY MYOPATHIES
Authors: V. Leclair, M. Holmqvist, A. Notarnicola, O. Krysturfkova, H. Mann, H. Andersson, L. P. Diederichsen, J. Vencovský, I. E. Lundberg, R. Steele, M. Hudson
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> The complex interactions amongst dysphagia, cancer, and mortality in idiopathic inflammatory myopathies (IIM) have never been studied. <h3>Objectives</h3> The aim of this study was to investigate the hypothesis that cancer can modify the effect of early dysphagia exposure on all-cause mortality in IIM patients. <h3>Methods</h3> A cohort of adult IIM patients with documented dysphagia exposure within 6 months of disease onset were identified from clinical registries in five countries (Sweden, Canada, Czech Republic, Denmark, and Norway). Mortality rates including 95% CI were calculated. Crude and adjusted mortality rates in IIM patients exposed to dysphagia or not were compared with Kaplan Meier curves and Cox proportional hazard models. To explore possible effect modification of cancer on the association between dysphagia and mortality, an adjusted Cox proportional hazard model stratified on cancer status and including an interaction term between dysphagia and cancer was performed. <h3>Results</h3> This study included 230 IIM adult individuals with a mean±SD age at diagnosis of 57±15 years and a mean±SD disease duration of 3±2 months. Of those, 146 (64%) were women, 122 (54%) had severe disease at baseline, 29 (13%) had cancer in the 3 years preceding IIM onset or within 6 months after IIM onset and 112 (49%) had dysphagia. When comparing the subjects unexposed or exposed to dysphagia, interstitial lung disease was less frequent (25 vs 58%), with more dermatomyositis (56 vs 28%) and less anti-synthetase syndrome (10 vs 36%) in the group exposed to dysphagia. Mortality rates per 100 person-years for IIM patients exposed to dysphagia were 2.3 (95%CI 1.0-4.5) in those without cancer compared to 33.3 (95%CI 16.6-59.2) in those with cancer. Crude survival curves for dysphagia exposure stratified by cancer status were significantly different (p &lt;0.0001). The main effect of dysphagia exposure in IIM patients without cancer was HR 0.6 (95%CI 0.2-1.8) compared to HR 2.9 (95%CI 0.7-12.4) in those with cancer. Dual exposure to dysphagia and cancer significantly increased the risk of mortality relative to patients with neither condition (p-value interaction 0.05). <h3>Conclusion</h3> This is the first study to demonstrate effect modification of cancer on the association between dysphagia and mortality in IIM. This suggests that IIM patients with and without cancer are very different and that separate analyses for the 2 groups should be considered when the outcome of interest is mortality. <h3>Reference</h3> None. <h3>Legend</h3> Differences between survival probabilities compared using the log rank test. <h3>Disclosure of Interests</h3> Valérie Leclair: None declared, Marie Holmqvist: None declared, Antonella Notarnicola: None declared, Olga Krysturfkova: None declared, Heřman Mann Speakers bureau: AbbVie, Pfizer, Novartis, UCB, Celltrion, MSD, Janssen, Eli-Lilly, Consultant of: AbbVie, Sobi, Gilead, Pfizer, Grant/research support from: Abbvie, Helena Andersson: None declared, Louise Pyndt Diederichsen: None declared, Jiří Vencovský Speakers bureau: Abbvie, Biogen, Boehringer, Eli Lilly, Gilead, MSD, Novartis, Pfizer, Roche, Sanofi, UCB, Werfen, Consultant of: Abbvie, Argenx, Boehringer, Eli Lilly, Gilead, Octapharma, Pfizer, UCB, Grant/research support from: Abbvie, Ingrid E. Lundberg Shareholder of: Roche, Novartis, Consultant of: Corbus Pharmaceuticals, Inc, Astra Zeneca, Bristol Myers Squibb, EMD Serono Research &amp; Development Institute, Argenx, Octapharma, Kezaar, Orphazyme, Pfizer and Janssen, Grant/research support from: Astra Zeneca, Russell Steele: None declared, Marie Hudson: None declared.